GRiSO running on one cylinder?

I always thought you were supposed to check the valve clearances with ALL the valves closed ie at top of compression stoke. Not sure what difference it makes but it looks like you are doing the exhaust side with the inlet valves wide open ?? Or am I missing something ?

BTW I mean all valves closed on the cylinder you are adjusting ie you should be able to 'wiggle' both Exhaust and Inlet sides at that point as no valves are being pushed

paulbrice wrote:

BTW I mean all valves closed on the cylinder you are adjusting ie you should be able to 'wiggle' both Exhaust and Inlet sides at that point as no valves are being pushed

You are correct.  Procedure is checks done at TDC of compression with both sets of valves closed.  So when the bike suddenly started running on what seemed like one cylinder i rushed a check of the exhaust valves thinking exhaust valves are usually the issue, i had checked the valve clearances 2 weeks earlier and all was perfect so I skipped the intake valves, stupid me.  So the left exhaust was able to be wiggled and I paid no attention to the intake.  

I couldn't understand how I checked exhaust valves one week earlier, haven't run the bike more than a few minutes and now they are too tight.  Ive come to believe i must have checked the left cylinder at the wrong point of the engine cycle (I was tired, frustrated and rushing.....my mistake).

What the videos show is the left cylinder exhaust valves close at a different point in the cycle than the right does.  At TDC of the exhaust stroke the left side exhaust valves are already completely closed while the right is closing well past TDC on the exhaust stroke.  

My hypothesis, aside from my boneheaded error in checking a week ago when problem arose, is the cams are somehow out of phase.  Lets say the left side exhaust valves are closing too early then that would mean they are opening too early.  That would explain why they are suddenly too tight and why I was able to check them at the wrong TDC.  

Like I said I checked all the valves two weeks before the initial problem arose and everything was perfect.  I rode the bike about 200 miles in that two weeks suddenly the exhaust valves are wildly out of adjustment.  By wildly I mean over .10mm on the exhaust.

ok got it.....couple thoughts:

1. I can see how one cam or both could slip out of sync during cam box removal & refit and this is known issue sometimes when cam is one tooth out on chain (chain drops off lower sprocket & pulls back to another - or top slips). This seems to hurt performance badly even with one tooth out !. If bike was running good (so cams lined up) then changed because cam slipped during operation, it implies cam tensioner has loosened/broken/failed and let chain move - not sure that's even possible within the limits of the slack created but if so then that's dangerous state......
2. Chain can't move without taking away all the slack as the sprockets are pinned and shouldn't move but I guess someone could leave off the pin and the sprocket could rotate (I thought there were other locating pins that are less deep but can't remember.
3. Valve clearances are miles out but not sure how/why that could happen except for flat tappet engine

So suggest you open the rubber bung and look for the TDC mark; remove the cam sprocket cover and check the alignment of the sprockets at TDC as below pic ....our of whack is very obvious; and finally check the tensioner is engaged

[You must be registered and logged in to see this image.]

A cam sprocket bolt might have come loose, there are holes in the oil flinger which might then have lined up with the pin. Just thinking aloud...

The "rubber bung"is actualy made of aluminium Paul

Unless somebody shifted the period table into neoprene land I don't think - at least on my bike the TDC window to the flywheel is rubber thru-and-thru....and goes in here

[You must be registered and logged in to see this image.]

BTW all the symptoms from start of this thread seem similar to previous one where the sprocket was installed out of sync by a tooth out on one side.....makes sense that one side won't run properly and bike won't rev...so guessing tensioner has failed due to oil blockage or something & one side is running out of kilter valve timing.

Sorry Paul, thought you meant the cap with o-ring retaining the camshaft sprocket

I tried finding the TDC mark many years ago and was told to forget it.  Can you show me what I'm looking for.  There is nothing i can see on the flywheel that comes close to marking TDC of either cylinder.  

When I pop the the breather cover off the rear of the cylinder i cannot see the sprocket as you can in your picture.  Do I need to remove the bolt and oil flinger to see the timing marks on the sprocket?  It does look like a pin is not seated, let me see if I can get an image up.  

[You must be registered and logged in to see this image.]

Exactly what I thought, the retaining pin for the sprocket has come through one of the stupid holes in the oil fling.

Carefully take out the pin protruding through the fling while loosing up the bolt for a start, don't let it fall down inside the engine!!!

Your problem is almost solved

Leave the sprocket in place, is the piston in compession TDC now? If not do that first. Pry out the retaining pin, it should be loose. remove the bolt and oil flinge while retaining the sprocket and chain in place. Make sure the correct hole (L for left) in the sprocket lines up with the hole beneath it in the camshaft. Replace the pin, it has to be flush with the sprocket. Use some locktite on the bolt and reinsert together with the oil flinge, make sure the holes in the flinge do not line up with the pin. Torque the bolt to the correct setting.

The TDC mark is on the flywheel - look on RHS as you sit on bike for a rubber bung down near the clutch/flywheel housing. As Klaas says (well thought Klaas) it looks like the pin that you can see in my picture has slipped out & allowed cam to move relative to sprocket (my picture has shield & the sprocket bolt removed but you can see the same pin sitting LEVEL with the outside of the sprocket). That pin should be held in by the shield and not sticking out; BTW I think you lucked out as the shield is holding the timing and if it had gone completely you would likely have screwed valves with piston.

Assuming your sprocket has slipped around the cam then you need to do following but suggest you read Pete's cam box removal thread to do it properly:
- Get the cylinder exactly at TDC at compression point using the flywheel marking (or screwdriver in plughole)
- go through the procedure to slacken the tensioner (will depend which side is way off how you do this as worst scenario will be tank off & undo the big tensioner bolt)
- carefully remove the sprocket bolt & the shield WITHOUT DROPPING PIN IN THE ENGINE
- tie the chain up to stop it dropping in
- put sprocket back on cam properly with pin in place
- rotate sprocket whilst ratcheting chain around until the cam lines up per my picture
- refit the chain & sprocket and shield properly
- reset the valve timing
- check other side
-

I see where Klaas is going and he's right if the chain hasn't actually slipped; you just need to return the sprocket to right place - soz for suggesting too much work !

Only the sprocket moved Paul

Now let's hope non of the valves hit the piston and are damaged...

Your right it should be dead easy (as long as don't drop the pin in the engine). Hopefully valves will be OK as previous threads with 1 tooth shifted didn't have any issues....

According to my pictures the pin is 3-4 teeth away from the oil plate holes one way and 6 teeth the other way (gulp)....hopefully it slipped the shorter distance

Hard to tell Paul as the pin is not connected to the sprocket at the moment and we can't see through the oil flinge. When the bolt is loosened up further the camshaft will move to almost the right position on its own because it's stress free when all valves are closed.

Jesus wept! Who's been working on this thing?

Pete Roper wrote:

Jesus wept! Who's been working on this thing?

Other than performing the basic maintenance work, valve clearances, throttle body balancing and replacing a few leaking o-rings as far as I'm aware no one has been in the engine since i bought it. Oh and a bad gasket on the oil pan extension that gave me a low oil pressure warning light, nothing has been done to the motor.

I'll attempt to tear into this later tonight when I have some free time. Thank you all for your help.

Almost forgot, make the chain tension free as described in the following article before you start removing things:

[You must be registered and logged in to see this link.]

Oh, forgot to ask....... I know where the inspection hole is to see the flywheel but I have never and still cannot find any marks indicating TDC or any other indicator.  Can anyone post a picture or explain what Im looking for?????

I have never removed that piece of shit but maybe Pete can tell you the relation between RH and LH TDC in correlation to cam position, you have to be at the right TDC before starting anything, markings on the flywheel won't help you one bit in finding it as we are talking 4-stroke here.